Support validation timer along mapping timer

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Is your feature request related to a problem? Please describe.
I am not seeing the "hours spent mapping" updated when I do validation. I suppose validation is not considered mapping for this timer.

Describe the solution you'd like
Implement the same timing mechanism to validation, and in https://tasks.hotosm.org/contributions to display hours spend validating

Additional context
Some people do mapping for corporate events and need to report hours. If validation isn't tracked it discourages those capable to validate in validating.